A wide variety of mechanical refrigeration systems are in use currently in a wide variety of applications. These applications include refrigerators, heat pumps, and air conditioners used both in vehicles and in buildings. The vast majority of mechanical refrigeration systems operate according to similar, well known principles, employing a closed-loop fluid circuit through which refrigerant flows.
Refrigerants are liquid substances that vaporize at low temperatures and are used in mechanical systems to deliver a cooling effect or for heat transfer. Refrigerants absorb heat via evaporation from one area and reject it via condensation into another area. A desirable refrigerant provides an evaporator pressure as high as possible and, simultaneously, a condenser pressure as low as possible. High evaporator pressures imply high vapor densities, and thus a greater system capacity for a given compressor. However, the efficiency at the higher pressures is lower, especially as the condenser pressure approaches the critical pressure. It has generally been found that the maximum efficiency of a theoretical vapor compression cycle is achieved by fluids with low vapor heat capacity, associated with fluids with simple molecular structure and low molecular weight.
Refrigerants must satisfy a number of other requirements as best as possible including compatibility with compressor lubricants and the materials of construction of refrigerating equipment, toxicity, environmental effects, cost availability, and safety.
The fluid refrigerants commonly used today typically include halogenated and partially halogenated alkanes, including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HFCFs), and less commonly hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs). A number of other refrigerants are known, including propane and fluorocarbon ethers. Some common refrigerants are identified as R11, R12, R22, R500, and R502, each refrigerant having characteristics which make it suitable for different types of applications. Because of the different temperature requirement sin different industries, differing refrigerants having different boiling points may all be brought to the same distributor. For example, R22 is of particular interest in that it is commonly used in commercial air conditioning systems, which often must be purged to conduct repairs. This R22 is collected in transfer vessels, also known as recovery cylinders, which hold about 30-50 pounds of refrigerant. This refrigerant is generally mixed with compressor lubricant oil, and may be contaminated with water, grit, or other materials.
During usage, it is important that the refrigerants be kept relatively free of contaminants, including foreign matter such as particulates, water and air. It is vital that hermetic integrity of the refrigerant system be maintained, both to retain the refrigerants and to prevent influx of undesired elements. When the refrigerants become contaminated, though influx of undesired elements, or breakdown of components, it becomes necessary to replace or purify the refrigerants. Contaminants within a refrigerant are thus substances that render the refrigerant impure. They include gaseous substances such as non-condensables, liquids such as water and solid particulates such as metal fillings. Contaminants also include chloride ions, acids and various other residues that result when hermetically sealed compressor motors fail while electrically charged, often with burned wire insulation. Contamination is generally measured via various laboratory instruments. Air conditioning/refrigeration original equipment manufacturers and standards organizations specify the percent of contamination allowable within equipment.
Mechanical refrigeration systems periodically require servicing. This servicing often takes the form of the addition of refrigerant into the system to replace refrigerant which has escaped from the system. Other servicing often takes the form of repairs to, or replacements of components in the system such as compressors, evaporators, filters, dryers, expansion valves and condensers.
Before adding refrigerant, or repairing or replacing one or more components, it is often necessary to remove the refrigerant remaining in the system. Typically, this remaining refrigerant is removed and stored in transfer vessels.
Transfer vessels are U.S. Department of Transportation ("U.S. D.O.T.") approved metal container used for the withdrawal, storage and transport of recovered refrigerants. They are certified by the manufacturer to withstand the design ratings required by the U.S. D.O.T. Transfer vessels are also known as recovery vessels, recovery cylinders, returnable shipping containers or simply "cylinders". Recovery cylinders are manually carried to the recovery site hence are typically restricted to the 30-50 lb. weight capacity classifications. These are specific labeling regulations for recovery cylinders and they are painted gray with yellow tops. These cylinders are generally characterized by a combined liquid/vapor valve located on top and many are equipped with reed switches that are used to shut off recovery equipment upon reaching maximum fill, which is a liquid level of 80%. A dip tube is employed internally to allow liquid removal without inverting the cylinder. However, this dip tube often does not allow complete withdrawal of liquid refrigerant from the transfer vessel. Typically, transfer vessels are not feature-rich, as they may be subject to exchange or substantial hiatus during processing. Therefore, sophisticated couplings, valves, gauges and the like are not commonly included, and the dip tubes, discussed below, may be inoperative or only partially functional. Because of the exchange or delay, these transfer vessels generally meet a "least common denominator". According to the present invention, the transfer vessel is immediately returned to the user, so that advanced features, such as quick connect couplings, gauges, highly functional dip tubes, high quality valves and the like may be included. For example, a quick-connect valve will save time and wear on the valve fitting, a distant concern for an exchange transfer vessel.
Dip tubes 3 are employed by the refrigerant recovery industry to provide an expeditious evacuation of a transfer vessel 1. The dip tube 3 is generally a metal or plastic hollow elongated cylindrical structure located internal to the transfer vessel 1. An external valve assembly 4 is mounted on top of the tank, from which the dip tube 3 extends downward. The dip tube's other end is as close to the transfer tank's bottom as feasible without risking blockage by the bottom or perhaps solid contaminants. Operation of the externally mounted valve 4 allows liquid refrigerant to be sucked or drawn out of the transfer vessel 1 without manually inverting the cylinder. A full transfer vessel 1 holds 80% of its volume in the liquid phase 2 with the remaining 20% at the top in a gaseous state. Without a dip tube 3, a top-only withdrawal process would be time consuming due to the differing densities and the need to vaporize refrigerant for withdrawal from the transfer vessel and then recondense it.
Hose fittings used for refrigerant recovery have been standardized to assist the development of the industry, and to prevent accidental filling of a transfer vessel with the wrong contents. The standard transfer vessel will mate with a SAE standard J639 fitting, which is 7/16 inch, 20 thread and is used for all common refrigerants except R-134a. The fitting on the transfer vessel is generally formed of brass.
Typically, a transfer vessel 1 filled with recovered refrigerant 2 is brought to a distributor. The distributor holds the transfer vessel for a recycler, who transports the transfer vessel to its facility. At the facility, as shown in FIG. 1, the content of the transfer vessel 1 is first connected to a fitting 7 and qualitatively analyzed for content by a qualitative analyzer 10 to determine a type and purity of the refrigerant 2. The transfer vessel is then disconnected from the qualitative analyzer 10, and the weight of the transfer vessel 1 is then recorded from a scale 19. The transfer vessel 1 is then connected to another fitting 8, and the refrigerant 2 removed, using an evacuation pump 12 and transferred into a storage reservoir 15. After complete evacuation, the weight of the transfer vessel 1 is again measured using the scale 19, and the difference calculated. The value of the refrigerant 2 is then calculated based on the qualitative analysis, weight, and attributed value. In this system, the valve 4 must be connected to two different fittings 7, 8, and the value calculated from various device outputs.
Infrequently, refrigerants may become mixed or mislabeled. Such mixtures may be very difficult to separate or reclaim, and further a small amount of an inappropriate or contaminating refrigerant may contaminate a large amount of pure refrigerant. This contamination makes the entire lot unsuitable for use and requires expensive purification of the entire lot. The costs involved in remediating such potential contamination are such that the transfer vessels are normally transported to a recycling facility for testing before they are admixed into larger containers. This leads to the problems that each separate transfer vessel must be shipped from a distributor's office or facility, tracked and the value accounted for, and then the emptied transfer vessels must be reshipped back to their owner or originator.
It is believed that refrigerants, especially chlorofluorocarbons (CFCs), used in vapor compression cooling systems (i.e., refrigeration systems) have a detrimental effect on the ozone layer of the earth's atmosphere when released from the refrigeration system into the environment. To this end, Federal legislation has been exacted, commonly referred to as the Clean Air Act, that has mandated strict requirements directed toward eliminating the release of CFCs into the atmosphere. In fact, after Jul. 1, 1992 Federal Law make it unlawful for any person in the course of maintaining, servicing, repairing and disposing of air conditioning or refrigeration equipment, to knowingly vent or otherwise release or dispose of ozone depleting substances used as refrigerants, and imposes stiff fines and penalties will be levied against violators.
The refrigerant management business is thus subject to extensive, stringent and frequently changing federal, state and local laws and substantial regulation under these laws by governmental agencies, including the EPA, the United States Occupational Safety and Health Administration and the United States Department of Transportation. Among other things, these regulatory authorities impose requirements which regulate the handling, packaging, labeling, transportation and disposal of hazardous and nonhazardous materials and the health and safety of workers.
Pursuant to the Clean Air Act, a recovered refrigerant must satisfy the same purity standards as newly manufactured refrigerants in accordance with standards established by the Air Conditioning and Refrigeration Institute ("ARI") prior to resale to a person other than the owner of the equipment from which it was recovered. The ARI and the EPA administer certification programs pursuant to which applicants are certified to reclaim refrigerants in compliance with ARI standards. Under such programs, the ARI issues a certification for each refrigerant and conducts periodic inspections and quality testing of reclaimed refrigerants. The ARI standards define a level of quality for new and reclaimed refrigerants which can be used in new or existing refrigeration and air-conditioning equipment. The standard is intended to provide guidance to the industry, including manufacturers, refrigerant reclaimers, and the like. Contaminated refrigerant can result in the failure of refrigeration system components such a the compressor.
To avoid releasing these fluorocarbons into the atmosphere, devices have been constructed that are designed to recover the refrigerant from the refrigeration system. Examples of such a refrigerant recovery devices are shown in U.S. Pat. Nos. 4,942,741; 4,285,206; 4,539,817; 4,364,236; 4,441,330; 4,476,668; 4,768,347; and 4,261,178.
The increasing cost of CFC refrigerants and the prohibition against environmental release have created a need for effective refrigerant recycling, recovery and reclamation equipment (hereinafter referred to as "recycling equipment"). In general terms, recycling equipment collects and reuses the refrigerant of a refrigeration system that has broken down and is need of repair or one that simply requires routine maintenance involving the removal of refrigerant. However, it should be noted that the terms "recover," "recycle" and "reclaim" have significantly distinct definitions in the art and that each definition connotes specific performance characteristics of a particular piece of recycling equipment.
"Recover" means removing refrigerant, in any condition, from a system and storing it in an external container without necessarily testing or processing it in any way. Recovery processes are well known, and often the refrigerant is recovered during system repair and used to recharge the source system after repair. Thus, where for some reason the source system is not immediately recharged, the recovered refrigerant, which is often not particularly contaminated, is removed. "Recycle" means to clean recovered refrigerant for reuse by separating moisture and oil and making a single or multiple passes through devices, such as replaceable core filter-dryers, which reduce moisture, acidity and particulate matter that have contaminated the refrigerant. A recycling system does not seek to separate mixed refrigerants or to assure product purity. Finally, "reclaim" means to reprocess the recovered and/or recycled refrigerants to new product specifications by means which may include distillation. Chemical analysis of the refrigerant is typically required to determine that appropriate product specifications are met. Thus, the term "reclaim" usually implies the use of processes or procedures available only at a reprocessing or manufacturing facility. However, portable reclamation systems are available.
There are a number of known methods and apparatus for separating refrigerants, including U.S. Pat. Nos. 2,951,349; 4,939,905; 5,089,033; 5,110,364; 5,199,962; 5,200,431; 5,205,843; 5,269,155; 5,347,822; 5,374,300; 5,425,242; 5,444,171; 5,446,216; 5,456,841; 5,470,442; and 5,534,151. In addition, there are a number of known refrigerant recovery systems, including U.S. Pat. Nos. 5,222,369; 5,226,300; 5,243,831; 5,245,840; 5,263,331; 5,272,882; 5,277,032; 5,313,808; 5,327,735; 5,353,603; 5,359,859; 5,363,662; 5,379,607; 5,390,503; 5,442,930; 5,195,333; 5,189,889; 5,176,008; 5,167,126; 5,032,148; and 5,044,166. Also known are refrigerant property analyzing systems, as shown in U.S. Pat. Nos. 5,371,019; 5,469,714; and 5,514,595.
After a period of use, refrigerants are commonly contaminated with compressor oil, water, other refrigerants, and various contaminants. In this case, contractors and HVAC maintenance workers must transfer used refrigerant into a transfer vessel, which, if not returned to the source refrigeration system, is then returned to a distributor. Generally, the distributor presently provides a receipt for the vessel, which is then shipped to a recycler/reclaimer, who qualitatively assays the refrigerant and determines the quantity. The qualitative assay and amount determine the value of the used refrigerant, which is then accounted to the source of the refrigerant. This known process is cumbersome, requiring the distributor, contractor or HVAC maintenance company to have multiple refrigerant transfer vessels available during the shipping analysis and return of the emptied vessel. Further, there may be a substantial accounting delay.
U.S. Pat. No. 5,231,841 relates to a refrigerant charging system which determines the mass amount of refrigerant charged by determining the volume of refrigerant charged, the density of the refrigerant based on its pressure as it is charged, and determines the mass amount charged from the determined density and pressure. The apparatus has a pressure compensated flow valve and determines the volume of refrigerant charged based on the amount of time refrigerant has flowed through the constant flow valve. The type of refrigerant being charged can be selected from a plurality of refrigerant types and the apparatus has a memory in which data related to density and flow characteristics of each refrigerant type is stored. The apparatus uses the data for the selected refrigerant to determine the mass amount of refrigerant charged. The apparatus further determines that the refrigerant supply tank is empty when its pressure decay exceeds a predetermined amount. The apparatus has a manifold in which the constant flow valve is mounted and the apparatus can be made as a portable, hand carried unit. The apparatus can also be used as a mass flowmeter.
Thus, there is a need for an apparatus and method for immediately valuing and removing refrigerant from a transfer vessel at a point of sale location, without need for many manual steps by the operator.